Wet station apparatus having quartz heater monitoring system and method of monitoring thereof

ABSTRACT

A wet station apparatus used for cleaning and wet etching a semiconductor wafer includes a chemical container for holding a chemical solution, a temperature measuring device for measuring a temperature of the chemical solution, a temperature control unit for comparing the temperature measured by the temperature measuring device with a predetermined reference temperature value, and outputting the result as a control signal, a quartz heater for heating the chemical solution, a power supply controller for receiving the control signal and adjusting the power supplied to the quartz heater, and a power switch connected to the power supply controller, for receiving a heating initiation signal and switching power to the quartz heater, wherein a heater monitoring system is further provided for monitoring the operating states of the quartz heater and the power supply controller and notifying an operator of any problems.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of application Ser. No. 08/735,454,filed Oct. 23, 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wet station apparatus used forcleaning or etching a semiconductor wafer, and more particularly, to awet station apparatus having a quartz heater monitoring system and amethod of monitoring thereof.

2. Background of the Related Art

In order to clean or wet etch a semiconductor wafer, a chemical solutioncontained in a chemical bath of the wet station apparatus needs to bepreheated to an appropriate temperature. Presently, a heating element isused for heating the chemical bath. However, if the heating elementdirectly contacts the chemical solution, it is likely to be eroded anddamaged by the chemical solution. Also, the chemical solution can becontaminated by undesired impurities existing on the surface of theheating element. Accordingly, to prevent these problems, the heatingelement is put into a sealed quartz tube. This type of heating unit iscalled a quartz heater.

FIG. 1 is a schematic view illustrating a conventional wet stationapparatus. The conventional apparatus, as shown in FIG. 1, includes: achemical solution 10 which is used for cleaning or wet etching issemiconductor wafer, a chemical container 20 for holding the chemicalsolution 10, a temperature measuring device 30 for measuring thetemperature of the chemical solution 10, a temperature control unit 40for comparing a temperature measured by the temperature measuring device30 with a predetermined reference temperature value and outputting theresult thereof as a control signal N1, a quartz heater 50 for heatingthe chemical solution 10, a power supply controller 60 for receiving thecontrol signal N1 and adjusting the power supplied to the quartz heater50, a power switch 70 connected to the power supply controller 60 forswitching power to the quartz heater 50, a Teflon coverlet 80 on which awafer cassette is placed so as to prevent the quartz heater fromdirectly contacting the wafer cassette during a cleaning or etchingprocess, and a power connector 90 for connecting the quartz heater 50with the power supply controller 60 and power switch 70.

Here, since the quartz heater 50 is located in the chemical solution 10,a conventional wet station apparatus generates the following problems.

First, if the quartz heater 50 is exposed to the chemical solution 10for a long time, the quartz tube of the quartz heater 50 reacts with thechemical solution 10. Accordingly, pinholes are apt to form on thesurface of the quartz tube or the quartz tube becomes very fragile.Thus, the heating element in the quartz tube 50 is easily eroded byexposure to the chemical solution 10, and the chemical solution 10 iscontaminated by undesired impurities from the heating element.

Also, since the Teflon coverlet 80 covers the quartz heater 50, it isdifficult to detect the damage of the quartz tube by visual inspection.Furthermore, a conventional wet station apparatus has no way ofautomatically detecting a damaged quartz tube, which results in severeaccidents occurring during the process.

Second, in case where several quartz heaters are provided, even though aheating element of one quartz heater among them is eroded by thechemical solution and then disconnected, the process is continued withthe remaining quartz heaters. Accordingly, the preheating time isincreased, whereby processing time is also increased.

Third, in case that the power supply controller 60 malfunctions, becausethe conventional apparatus has no way of promptly detecting the problem,a warning signal is not generated until the quartz heater 50 hasoverheated.

As described above, because the conventional wet station apparatus, usedfor the cleaning and wet etching operations related to a semiconductorwafer, has no way of promptly detecting the damage to the quartz tube ofthe quartz heater nor the disorders of the power supply controller,severe accidents can occur during the process.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a wetstation apparatus having a quartz heater monitoring system for promptlydetecting and reporting disorders which are prone to occur in a quartzheater or power supply control means.

To achieve these and other objects, the present invention provides for awet station apparatus, used for cleaning and wet etching a semiconductorwafer, comprising: a chemical container for holding a chemical solution;temperature measuring means for measuring a temperature of the chemicalsolution; temperature control means for comparing the temperaturemeasured by the temperature measuring means with a predeterminedreference temperature value, and outputting the result as a controlsignal; a quartz heater for heating the chemical solution; power supplycontrol means for receiving the control signal and adjusting powersupplied to the quartz heater; a power switch connected to the powersupply control means, for receiving a heating process initiation signaland then switching power to the quartz heater in response thereto; and aquartz heater monitoring system for monitoring operating states of thequartz heater and the power supply control means, respectively, andnotifying a user of abnormalities in the respective operating states.

In addition, the quartz heater monitoring system comprises: firstcomparing means for receiving the control signal output from thetemperature control means, and analyzing the control signal toselectively output one of a first signal for increasing the powersupplied to the quartz heater and a second signal for decreasing thepower supplied to the quartz heater; a current-to-voltage converterinstalled between the quartz heater and the power switch, for convertinga current flowing into the quartz heater to a voltage; second comparingmeans for comparing a voltage signal input from the current-to-voltageconverter with a predetermined reference value, and outputting one of athird signal if the amount of current flowing into the quartz heater islower than the predetermined reference value and a fourth signal if theamount of current flowing into the quartz heater is higher than thepredetermined reference value; state judgment means for receiving theoutput signals from the first and second comparing means, and analyzingthe operating states of the quartz heater and the power supply controlmeans; and indicating means for notifying a user of abnormalities withinthe operating state of one of the quartz heater and the power supplycontrol means, analyzed by the state judgment means.

Additionally, the state judgement means comprises: a first analyzingunit for outputting one of a fifth, sixth, or seventh signal to saidindicating means, wherein the fifth signal, indicating a normaloperating state of the quartz heaters and the power supply controlmeans, being outputted if the first comparing means outputs the firstsignal and the second comparing means outputs the third signal, or thefirst comparing means outputs the second signal and the second comparingmeans outputs the fourth signal, and wherein the sixth signal,indicating an abnormal operating state of the quartz heater, beingoutputted if the first comparing means outputs the first signal and thesecond comparing means outputs the fourth signal, and wherein theseventh signal, indicating an abnormal operating state of the powersupply control means, being outputted if the first comparing meansoutputs the second signal and the second comparing means output thethird signal; and signal interrupting means for interrupting the heatingprocess initiation signal to stop the power supplied to the power switchwhen one of the sixth and seventh signals is detected.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore apparent by describing in detail a preferred embodiment thereofwith reference to the attached drawings in which:

FIG. 1 is a schematic view showing a conventional wet station apparatus;and

FIG. 2 is a schematic view showing a wet station apparatus having aquartz heater monitoring system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the present invention will be described indetail with reference to the attached drawings.

Referring to FIG. 2, the wet station apparatus according to a preferredembodiment includes: a chemical solution 11 used for cleaning or wetetching a semiconductor wafer, a chemical container 21 for holding thechemical solution 11, and a temperature measuring unit 31, a portion ofwhich is immersed in the chemical solution 11, for measuring thetemperature of the chemical solution 11. Quartz heater 51 heats thechemical solution 11. Temperature control unit 41 compares thetemperature measured by the temperature measuring unit 31 with apredetermined reference temperature value and outputs the result thereofas a control signal N3. Power supply control unit 61 receives thecontrol signal N3 and adjusts the power supplied to the quartz heater51. Teflon coverlet 81, immersed in the chemical solution 11, supports awafer cassette so that it does not directly contact the quartz heater51. Power connector 85 connects the quartz heater 51 with the powersupply control unit 61.

In this embodiment, a power switch 71, connected to the power supplycontrol unit 61, receives a heating process initiation signal N2 andswitches power to the quartz heater 51. First comparing unit 91 receivesthe control signal N3 from the temperature control unit 41 anddetermines whether to increase or decrease power to the quartz heater 51based on the control signal N3. A first signal is output for increasingthe power, and a second signal is output for decreasing the power to thequartz heater 51. Current-to-voltage converter 101, installed betweenthe quartz heater 51 and the power switch 71, converts the currentflowing into the quartz heater 51 to voltages. Second comparing unit 201compares the voltage signals that are output from the current-to-voltageconverter 101 with a predetermined reference value. The second comparingunit then outputs a third signal when the current flowing into thequartz heater 51 is lower than the predetermined reference value oroutputs a fourth signal if it is higher. State judgment unit 301receives the output signals from the first and second comparing units 91and 20 and then determines the operating state of the quartz heater 51and the power supply control unit 61. Indicator 401 indicates anabnormal operating state within the quartz heater 51 or the power supplycontrol unit 61.

The state judgment unit 301 will now be discussed in greater detail. Thestate judgment unit 301 includes a first analyzing unit 311 foranalyzing the signals input thereto from the first and second comparingunits 91 and 201, respectively. Depending on the analysis, the firstanalyzing unit 311 outputs a fifth, sixth or seventh signal (describedfurther below) to the indicator 401. Signal interrupting device 321interrupts the supply of power to the quartz heater 51 if an abnormalityoccurs in the operating state of either the quartz heater 51 or thepower supply control unit 61. In the event that the heating processinitiation signal N2 is interrupted, a second analyzing unit 331determines whether the operating states of either the quartz heater 51or the power supply control unit 61 are normal, regardless of signalsoutput from the first and second comparing units 91 and 201,respectively, via the signal interruption device 321. The secondanalyzing unit 331 then transmits the appropriate signal to theindicator 401.

The above-mentioned fifth, sixth and seventh signals, which areoutputted from the first analyzing unit 311, are determined as follows.The fifth signal, indicating a normal state of the quartz heater 51 andpower supply control unit 61, is output if the first comparing unit 91outputs the first signal and the second comparing unit 201 outputs thethird signal, or the first comparing unit 91 outputs the second signaland the second comparing unit 201 outputs the fourth signal. The sixthsignal, indicating an abnormal state of the quartz heater 51, is outputif the first comparing unit 91 outputs the first signal and the secondcomparing unit 201 outputs the fourth signal. The seventh signal,indicating an abnormal state of the power supply control unit 61, isoutput if the first comparing unit 91 outputs the second signal and thesecond comparing unit 201 outputs the third signal.

The indicator 401 can either use an alarm for aurally warning a user ora lamp for visually warning the user. Also, a control signal of 0-5V,0-10V or 0-24V can be used as the control signal N3 in case that thepower supply control unit 61 is a solid state relay unit (SSR unit).Furthermore, the current-to-voltage converter 101 converts the current,flowing into the quartz heater 51, into a voltage within the range of0-5V, to sense the variation of current flowing into the quartz heater51.

Referring to the embodiment of the present invention as described above,unlike the conventional wet station apparatus, the wet station apparatusof the present invention further comprises a heater monitoring systemfor promptly detecting abnormalities with either the quartz heater orthe power supply control unit and notifying an operator, therebyincreasing the speed of the process, and at the same time, preventingsevere accidents from occurring.

It should be understood that the invention is not limited to theillustrated embodiment and that many changes and modifications can bemade within the scope of the invention by a person skilled in the art.

What is claimed is:
 1. A method of monitoring a quartz heater in a wetstation apparatus used for cleaning and wet etching a semiconductorwafer, the method comprising the steps of:measuring a temperature of achemical solution; comparing the temperature measured with apredetermined reference temperature value, and outputting the result asa control signal; heating said chemical solution with a quartz heater;receiving the control signal output from a temperature control means,and analyzing the control signal to selectively output one of a firstsignal for increasing the power supplied to said quartz heater and asecond signal for decreasing the power supplied to said quartz heater;receiving a heating process initiation signal, by a power switchconnected to a power supply control means, for switching power to saidquartz heater in response thereto; and converting a current flowing intosaid quartz heater to a voltage signal using a current-to-voltageconverter installed between said quartz heater and the power switch;comparing the voltage signal input from said current-to-voltageconverter with a reference value, and outputting one of a third signalif the amount of current flowing into said quartz heater is lower thansaid reference value and a fourth signal if the amount of currentflowing into said quartz heater is higher than said reference value; andmonitoring and analyzing operating states of said quartz heater and saidpower supply control means, respectively, and notifying a user ofabnormalities in said respective operating states.
 2. A method ofmonitoring a quartz heater as claimed in claim 1, said monitoring stepcomprising the sub-steps of:flowing into said quartz heater is lowerthan said predetermined reference value and a fourth signal if theamount of current flowing into said quartz heater is higher than saidpredetermined reference value; selectively receiving the first, second,third, and fourth signals for analyzing the operating states of saidquartz heater and said power supply control means; and notifying a userof abnormalities within the operating state of one of said quartz heaterand said power supply control means in response to said first, second,third, and fourth signals.
 3. A method of monitoring a quartz heater asclaimed in claim 2, said selectively receiving step comprising thesub-steps of:outputting a fifth signal, indicating a normal operatingstate of said quartz heater and said power supply control means, if saidfirst signal and said third signal are received, or said second signaland said fourth signal are received; outputting a sixth signal,indicating an abnormal operating state of said quartz heater, if saidfirst signal and said fourth signal are received; outputting a seventhsignal, indicating an abnormal operating state of said power supplycontrol means, if said second signal and said third signal are received;and interrupting the heating process initiation signal to stop the powersupplied to the power switch when one of said sixth and seventh signalsis detected.
 4. A method of monitoring a quartz heater as claimed inclaim 3, further comprising the steps of:determining that the operatingstates of said quartz heater and said power supply control means arenormal, regardless of whether the sixth and seventh signals are detectedin case that said heating process initiation signal is interrupted; andproviding a normal operating signal to the user.